(Editor's note: Jeff Mapes is a political writer and blogger for The Oregonian who is completing a book about how cyclists are changing American cities.)

The Oregonian's lead story on that weird assault-by-bicycle - and a dip into the hundreds of passionate posts on the subject in the blogosphere - left me more convinced than ever of a simple proposition: change is hard and maybe nowhere more than out on the streets.

After all, where else in life do we routinely have to respond to potentially life-threatening situations in nano-seconds? Talk about lighting up your lizard brain.

In Portland, we're engaged in what many might see as a big experiment to make bicycles a major form of transportation. Cyclists now account for as many as 6 percent of commuters, more than in any other major American city.

In the part of Southeast Portland where Colin Yates, who was a driver in a car, said he was clobbered with a bike wielded by a rider who was angry at being admonished for running a red light, that number rises to more than 10 percent.

Almost all of this change has occurred in not much more than a decade and, judging from the passion of the posts I read today, folks are still adjusting.

There were usual rants from the motorists who think the streets should be reserved solely for automotive traffic - as well as from cyclists who are quick to immediately assume the driver somehow had to be at fault. .

But I was struck that many Portlanders are puzzling through how to make the new reality on our streets work. Several people who regularly cycle said they needed to exert more social pressure on cyclists who routinely run red lights and in general ignore traffic laws.

"I am an avid cyclist and I get cursed when I point out the failure to stop at a red light or stop sign," said one commentor on bikeportland.org. "We in the cycling community need to step up and police ourselves and follow the rules."

In the same fashion, it was easy to find harsh criticism of the rider, Steven McAtee, on the bikeportland.org blog. Many posters knew the driver, Yates, who until recently has been a mechanic at the Bike Gallery.

As a cyclist who is finishing a book on how bicyclists are changing American cities, I think we have a lot more cultural change to come. Cycling is mostly folk transportation now, practiced by people who often learn as they go.

You might say it's one form of transportation with lower barriers of entry: kids, homeless people, recovering alcoholics who have lost their license and lots of middle-class folks looking for a little exercise and a simple way to get to work. Bicycling education is only starting to get established in the schools and people often imitate what they see around them.

And hot heads are hot heads, whether on two wheels are four. So you might think of Sunday's violent incident as an inevitable extension of the road rage that's so common among motorists. It's the simple math of having more cyclists on the road.

What's ironic about today's headline, though, is it belies what is increasingly a common reality out on the streets. A lot of folks are getting along. Despite the rapid rise in the number of cyclists, crash rates have dropped. I've talked to numerous bike advocates from other cities who rave about the relative friendliness of Portland drivers.

I had a taste of that just this morning when I pedaled off from home - in a somewhat tentative mood after reading The Oregonian's story and having sampled the often venomous bite of the blogosphere.

What I ended up encountering were two motorists who voluntarily surrendered their right of way to let me quickly cross two busy arterials (thanks folks, but not necessary!). The downright mellow mood of the commute was captured by a young women I saw leisurely ride past in a colorful summer skirt with a big smile on her face.

Yes, it isn't always like that. The night before, at the height of rush hour, I had to contend with two motorists who blew through a stop sign and a young, bare-chested cyclist who almost smacked into me when he was running his own red light.